1. Field of the Invention
The present invention relates to a thin film transistor of a field effect type and, more particularly, to a field effect type thin film transistor which can also endure for high-speed use.
2. Related background art
In recent years, the characteristics of a thin film transistor (TFT) have been improved with the aid of the remarkable advancement of the amorphous semiconductor technology.
Hitherto, there has been known that the thin film transistor is formed by a multilayer material consisting of a first solid layer of a semiconductor or insulating material formed of non-monocrystalline material and a second solid layer which are alternately laminated. This thin film transistor is mainly used in the high frequency resistor circuit network, RC circuit network, and the like.
However, such thin film type transistors don't have a low threshold voltage (V.sub.th) nor a high field effect type mobility (.mu..sub.FE). Therefore, thin type transistor are desired which have excellent specifications regarding the threshold voltage and mobility which can be sufficiently used as a semiconductor material for a high speed device.